Objective: To explore the protective effects of Tibetan medicine Zuo-Mu-A Decoction(佐木阿汤, ZMAD) on the blood parameters and myocardium of high altitude polycythemia(HAPC) model rats. Methods: Forty male Wistar rats were randomly divided into 4 groups by a random number table, including the normal, model, Rhodiola rosea L.(RRL) and ZMAD groups(10 in each group). Every group was raised in Lhasa to create a HAPC model except the normal group. After modeling, rats in the RRL and the ZMAD groups were administered intragastrically with RRL(20 mL/kg) and ZMAD(7.5 mL/kg) once a day for 2 months, respectively; for the normal and the model groups, 5 mL of distilled water was administered intragastrically instead of decoction. Then routine blood and hematologic rheology parameters were taken, levels of erythropoietin and 8-hydroxy-2’-deoxyguanosine(8-OHd G) were tested, and ultrastructural change in the left ventricular myocardium was observed using transmission electron microscopy. Results: Compared with the model group, ZMAD significantly reduced the red blood cell count, hemoglobin levels, whole blood viscosity at low/middle shear rates, plasma viscosity, erythrocyte electrophoretic time, erythropoietin and 8-OHd G levels, and also increased the erythrocyte deformation index(P<0.05). There was no difference in all results between the RRL and the ZMAD groups. The cardiac muscle fibers were well-protected, mitochondrial matrix swelled mildly and ultrastructure changes were less prominent in the ZMAD group compared with the model group. Conclusion: ZMAD has significant protective effects on the blood parameters against HAPC, and also has the beneficial effect in protecting against myocardial injury. Objective: To explore the protective effects of Tibetan medicine Zuo-Mu-A Decoction (on ZMAD) on the blood parameters and myocardium of high altitude polycythemia (HAPC) model rats. Methods: Forty male Wistar rats were divided divided into 4 groups by a random number table, including the normal, model, Rhodiola rosea L. (RRL) and ZMAD groups (10 in each group). Every group was raised in Lhasa to create a HAPC model except the normal group. After modeling, rats in the RRL and the ZMAD groups were administered intragastrically with RRL (20 mL / kg) and ZMAD (7.5 mL / kg) once a day for 2 months, respectively; for the normal and the model groups, 5 mL of distilled water was administered routinely and hematologic rheology parameters were taken, levels of erythropoietin and 8-hydroxy-2’-deoxyguanosine (8-OHd G) were tested, and ultrastructural change in the left ventricular myocardium was observed using transmission electron microscopy. Resul ts: Compared with the model group, ZMAD significantly reduced the red blood cell count, hemoglobin levels, whole blood viscosity at low / middle shear rates, plasma viscosity, erythrocyte electrophoretic time, erythropoietin and 8-OHd G levels, and also the erythrocyte There was no difference in all results between the RRL and the ZMAD groups. The cardiac muscle fibers were well-protected, mitochondrial matrix swelled mildly and ultrastructure changes were less prominent in the ZMAD group compared with the model group. Conclusion: ZMAD has significant protective effects on the blood parameters against HAPC, and also the beneficial effect in protecting against myocardial injury.